Hi,
just a basic question, relevant to squid2.7, at least:
AFAIK, without looking into the src code, squid2.7 requests and caches
the complete object, before delivering the data to fulfill the first
range request.
Delivery might even start as soon as the data for the actual range
request is available.
Further range requests will be handled from the cached "complete object".
In case, this is correct, then it should also be valid using
storeurl_rewrite_program in squi2.7
The probability, that other parts of the cached "complete object" will be
reuested, is
quite high, so no
no need for something new.
This strategy might even be an advantage, in case, the range requests
for the same object vary in size, which might be dependent upon
connection speed.
Hey,
As far as I know squid serves 206 partial responses from cache only if the full
object exists in cache.
I can not follow the flow of execution in squid2.7, but I am not shure, that
you are correct.
These excerpts from squi2.7 MIGHT indicate, that transmission of
data for a range request to the client can start before the complete object is
cached:
squid.conf:
# TAG: range_offset_limit (bytes)
# Sets a upper limit on how far into the the file a Range request
# may be to cause Squid to prefetch the whole file. If beyond this
# limit Squid forwards the Range request as it is and the result
# is NOT cached.
#
# This is to stop a far ahead range request (lets say start at 17MB)
# from making Squid fetch the whole object up to that point before
<=============================
# sending anything to the client.
client_side.c:
clientCheckRangeForceMiss(StoreEntry * entry, HttpHdrRange * range)
{
/*
* If the range_offset_limit is NOT in effect, there
* is no reason to force a miss.
*/
if (0 == httpHdrRangeOffsetLimit(range))
return 0;
/*
* Here, we know it's possibly a hit. If we already have the
* whole object cached, we won't force a miss.
*/
if (STORE_OK == entry->store_status)
return 0; /* we have the whole object */
/*
* Now we have a hit on a PENDING object. We need to see
<===========================================
* if the part we want is already cached. If so, we don't
* force a miss.
*/
assert(NULL != entry->mem_obj);
if (httpHdrRangeFirstOffset(range) <= entry->mem_obj->inmem_hi)
return 0;
/*
* Even though we have a PENDING copy of the object, we
* don't want to wait to reach the first range offset,
* so we force a miss for a new range request to the
* origin.
*/
return 1;
}
I guess, Alex should have a definite answer.
--
Mit freundlichen Grüßen
Reiner Karlsberg
Ringerottstr. 50
45772 Marl
Germany
Tel.: (+49) (0)2365-8568281
Mob.: (+49) (0)1788904200
-----
This eMail does not contain any virus.
Von AVG überprüft - www.avg.de
Version: 2012.0.2242 / Virendatenbank: 3184/5862 - Ausgabedatum: 27.05.2013
